Operating notes for DHCPv6

  • A DHCPv6-relay message sent to any multicast address carries a hop limit of 32. The hop limit for DHCPv6 requests sent to a unicast address is determined by the ipv6 hop-limit <1–255> command at the global configuration level; Default: 64.

  • Multicast addresses reserved for DHCPv6 include the following:
    • FF02::1:2—All_DHCP_Relay_Agents_and_Servers

    • FF05::1:3—All_DHCP_Servers

  • DHCPv6 client and relay functions are mutually exclusive on a VLAN. Attempting to configure one of these functions on a VLAN while the other is already configured results in one of the following messages:
    • Cannot configure an IPv6 helper–address as DHCPv6 client is enabled on the VLAN.
    • Cannot enable DHCPv6 client as an IPv6 helper–address is configured on the VLAN.
  • The routing switch supports concurrent, independent operation of DHCPv4 and DHCPv6.

  • Operating limits:

    DHCPv6-relay feature


    Unique Helper addresses supported on the routing switch

    32 1

    Unique Helper addresses per VLAN interface



    If the same Helper address is used on multiple VLANs, it is counted as one address toward these maximums.